JP6939493B2 - Exhaust purification device for internal combustion engine - Google Patents

Description

The present invention relates to an exhaust gas purification device for an internal combustion engine.

The exhaust gas purification device for an internal combustion engine described in Patent Document 1 is provided in an exhaust passage and is a PM filter that collects particulate matter (hereinafter referred to as "PM". PM is an abbreviation for Particulate Matter) contained in the exhaust gas. It also has a differential pressure sensor that detects the front-rear differential pressure, which is the difference between the pressure on the upstream side of the exhaust gas from the PM filter in the exhaust passage and the pressure on the downstream side of the exhaust gas from the PM filter. The exhaust purification device for an internal combustion engine described in Patent Document 1 calculates a first estimated amount as an estimated amount of PM accumulated in a PM filter based on the operating state of the internal combustion engine, and PM detected by a differential pressure sensor. The second estimator is calculated as the estimator of PM deposited on the PM filter based on the differential pressure before and after the filter. Then, the larger value of the first estimated amount and the second estimated amount is calculated as the PM accumulated amount, which is the accumulated amount of PM accumulated in the PM filter. In the exhaust gas purification device for an internal combustion engine described in Patent Document 1, when the amount of PM deposited is equal to or greater than a predetermined amount, regeneration control for removing PM collected by the PM filter is started. In the regeneration control, the PM collected by the PM filter is burnt and removed by raising the temperature of the exhaust gas.

Further, the exhaust gas purification device for an internal combustion engine described in Patent Document 2 calculates a first estimated amount and a second estimated amount in the same manner as the exhaust gas purification device for an internal combustion engine described in Patent Document 1. With regard to these first and second estimators, when the second estimator is calculated, the first estimator is corrected based on the second estimator, and this is used as the PM deposition amount to obtain PM. It is used for regeneration control for removing PM collected by the filter.

Japanese Unexamined Patent Publication No. 2004-197722 Japanese Unexamined Patent Publication No. 2008-057443

If an abnormality occurs in the differential pressure sensor, the value of the second estimated amount calculated based on the detection signal of the differential pressure sensor may not be an appropriate value corresponding to the actual PM deposition amount. In this case, as described in Patent Document 2, if the first estimator is corrected based on the second estimator, the calculation accuracy of the PM deposition amount will also decrease. There is no disclosure in Patent Documents 1 and 2 regarding these points.

An exhaust purification device for an internal combustion engine for solving the above problems is provided in an exhaust passage of the internal combustion engine, and includes a PM filter that collects PM contained in the exhaust and a pressure on the upstream side of the exhaust from the PM filter. It is equipped with a differential pressure sensor that detects the front-rear differential pressure, which is the difference from the pressure on the downstream side of the exhaust from the PM filter, and is used as an estimated amount of PM accumulated in the PM filter based on the operating state of the internal combustion engine. It is an internal combustion engine exhaust purification device that calculates the first estimated amount and calculates the second estimated amount as the estimated amount of PM accumulated in the PM filter based on the front-rear differential pressure detected by the differential pressure sensor. Then, when the differential pressure sensor is abnormally determined based on the state of the differential pressure sensor during the period from the stop of the internal combustion engine to the start of the start of the internal combustion engine, the first is performed when the internal combustion engine is started. A correction process for correcting the estimated amount based on the second estimated amount is executed, and the larger value of the first estimated amount and the second estimated amount is calculated as the PM accumulated amount, and the PM accumulated amount is determined. When the amount is equal to or higher than the fixed amount, the filter regeneration control for burning and removing the PM collected by the PM filter is started.

In the above configuration, when the internal combustion engine is started, the first estimator calculated based on the operating state of the internal combustion engine is corrected based on the second estimator calculated based on the front-rear differential pressure of the PM filter. .. The front-rear differential pressure of the PM filter is detected by the differential pressure sensor. As for the differential pressure sensor, since the abnormality judgment is made based on the state in the period from the stop of the internal combustion engine to the start of the internal combustion engine, the abnormality judgment of the differential pressure sensor is made at the timing when the internal combustion engine is started. It is appropriate to do. Therefore, if it is the timing when starting the internal combustion engine, it is possible to calculate the second estimator supported by the normality of the differential pressure sensor, and it is possible to ensure the accuracy in the calculation of the second estimator. It will be possible. The first estimated amount is calculated based on the operating state of the internal combustion engine, and has a wide operating range that can be calculated. On the other hand, when the front-rear differential pressure detected by the differential pressure sensor and the amount of PM deposited on the PM filter have a correlation, the operating area of the internal combustion engine is limited, so that the second estimated amount can be calculated. The driving area is narrow. Since the influence of the amount of PM actually deposited on the PM filter is reflected in the front-rear differential pressure of the PM filter, the second estimator is actually deposited on the PM filter as compared with the first estimator. It is easy to reflect the amount of PM. Therefore, as in the above configuration, the first estimator having a wide calculable operating range is corrected based on the second estimator in consideration of the appropriate timing for determining the abnormality of the differential pressure sensor. Therefore, it is possible to suppress a decrease in the calculation accuracy of the PM deposition amount.

Further, in the exhaust purification device of the internal combustion engine, when the first estimated amount is larger than the second estimated amount, the first estimated amount is reduced and corrected in the correction process, and the first estimated amount is the first estimated amount. 2 When the amount is smaller than the estimated amount, the first estimated amount is increased and corrected in the correction process, and when the decrease correction is performed, the correction degree of the first estimated amount is increased as compared with the case where the increase correction is performed. It is desirable to make it smaller.

In the above configuration, when the first estimator is larger than the second estimator and when the first estimator is reduced and corrected, the first estimator is smaller than the second estimator. Therefore, the degree of correction of the first estimator is made smaller than that when the first estimator is increased and corrected. When the first estimator is larger than the second estimator, the first estimator is used as the PM deposition amount, which is a parameter for determining the execution of the filter regeneration control. Therefore, by reducing the degree of correction when the first estimator is reduced and corrected, even if a situation occurs in which the accuracy of the second estimator is lowered due to the influence of disturbance of the differential pressure sensor or the like, PM Sudden changes in the amount of deposit can be suppressed. As a result, when the first estimator is corrected based on the second estimator, it is possible to prevent the corrected first estimator from becoming less than the amount of PM actually deposited on the PM filter. And the PM deposition amount can be set appropriately.

Further, in the exhaust gas purification device of the internal combustion engine, when the first estimated amount is increased and corrected, the value of the corrected first estimated amount in one correction process is set to a value equal to the second estimated amount. Is desirable.

In the above configuration, when the first estimator is smaller than the second estimator and the first estimator is increased and corrected, the value of the first estimator after correction in one correction process is the second estimation. It is corrected so that it becomes a value equal to the amount. Therefore, the PM deposit amount is actually deposited on the PM filter as compared with the configuration in which the correction process is executed a plurality of times until the value of the first estimated amount becomes equal to the value of the second estimated amount and the amount is gradually increased and corrected. It becomes easy to avoid a state where the amount of PM is less than the amount of PM at an early stage.

Further, in the exhaust gas purification device of the internal combustion engine, when the first estimated amount is reduced and corrected, it is desirable to set an upper limit to the corrected amount of the first estimated amount in one correction process.
The detection signal of the differential pressure sensor may be disturbed due to some influence even when no abnormality has occurred. If the detection signal of the differential pressure sensor is disturbed, the second estimator may be calculated as an amount smaller than the amount of PM actually deposited on the PM filter.

According to the above configuration, when the first estimated amount is reduced and corrected, an upper limit is set for the correction amount. Therefore, it is difficult to reduce the value of the first estimator to a value equal to the second estimator in one correction process. As a result, the value of the first estimated amount can be gradually reduced to a value equal to the second estimated amount by executing the correction process a plurality of times. Therefore, it is possible to prevent the value of the first estimated amount after correction from becoming lower than the value of the actual PM accumulation amount due to the temporary disturbance of the detection signal of the differential pressure sensor, and the PM accumulation amount. Can be set appropriately.

Further, in the exhaust gas purification device of the internal combustion engine, the correction process is executed when the differential pressure sensor is determined to be normal by the abnormality determination, and when the differential pressure sensor is determined to be abnormal. It is desirable not to execute the correction process.

According to the above configuration, the correction process is performed when the differential pressure sensor is normal and the accuracy of the second estimator is guaranteed, and the differential pressure sensor is abnormal and the accuracy of the second estimator is guaranteed. If not, the correction process is not performed. Therefore, when the first estimator is corrected based on the second estimator, the corrected first estimator is set to a value that reflects the actual PM deposition amount as compared with the first estimator before the correction. be able to.

The schematic diagram which shows the structure of the exhaust gas purification apparatus of an internal combustion engine. Functional block diagram of the control device. A map showing the relationship between deviation and correction amount. A flowchart showing a flow of a series of processes related to the correction process. A flowchart showing a flow of a series of processes related to filter reproduction control. (A) to (e) are timing charts showing changes in each parameter due to changes in the operating state of the internal combustion engine when the differential pressure sensor is normal. (A) to (e) are timing charts showing changes in each parameter due to a change in the operating state of the internal combustion engine when an abnormality occurs in the differential pressure sensor.

An embodiment of an exhaust gas purification device for an internal combustion engine will be described with reference to FIGS. 1 to 7. In this embodiment, an example in which the exhaust gas purification device is applied to a gasoline engine as an internal combustion engine will be described.

As shown in FIG. 1, a plurality of combustion chambers 10A are provided in the engine body 10 of the internal combustion engine. The engine body 10 is provided with a fuel injection valve 11 for supplying fuel to each combustion chamber 10A. One fuel injection valve 11 is provided in each combustion chamber 10A. The exhaust gas purification device 100 of an internal combustion engine has an exhaust passage 20 connected to an engine body 10. Exhaust gas is discharged from the combustion chamber 10A into the exhaust passage 20. The exhaust passage 20 has a first exhaust pipe 21 connected to the engine body 10 and a first catalytic converter 22 connected to an end on the exhaust downstream side of the first exhaust pipe 21. An oxidation catalyst 30 is provided inside the first catalyst converter 22. The oxidation catalyst 30 oxidizes hydrocarbons (HC) and carbon monoxide (CO) contained in the exhaust gas to generate water and carbon dioxide.

A second exhaust pipe 23 is connected to the first catalyst converter 22 at an end on the downstream side of the exhaust gas. The second exhaust pipe 23 is provided with an exhaust temperature sensor 40 that detects the temperature of the exhaust gas. A second catalytic converter 24 is connected to the second exhaust pipe 23 at an end on the downstream side of the exhaust. A PM filter 31 is provided inside the second catalytic converter 24. The PM filter 31 collects PM contained in the exhaust gas. A third exhaust pipe 25 is connected to the second catalyst converter 24 at an end on the downstream side of the exhaust gas.

A differential pressure sensor 41 is provided in the exhaust passage 20. The differential pressure sensor 41 has an exhaust differential pressure detection unit 42, and an upstream side detection passage 43 and a downstream side detection passage 44, which are connected to the exhaust differential pressure detection unit 42, respectively. The upstream detection passage 43 is connected to a second exhaust pipe 23 between the oxidation catalyst 30 and the PM filter 31 in the exhaust passage 20. That is, the exhaust gas flowing between the oxidation catalyst 30 and the PM filter 31 flows into the upstream detection passage 43. Further, the downstream side detection passage 44 is connected to the third exhaust pipe 25 on the exhaust downstream side of the PM filter 31 in the exhaust passage 20. That is, the exhaust gas after passing through the PM filter 31 flows into the downstream detection passage 44. The pressure on the exhaust upstream side of the exhaust passage 20 acts on the exhaust differential pressure detection unit 42 through the upstream detection passage 43, and the exhaust downstream of the PM filter 31 in the exhaust passage 20 through the downstream detection passage 44. Side pressure acts. The exhaust differential pressure detection unit 42 detects the front-rear differential pressure ΔP, which is the difference between these pressures. The exhaust gas purification device 100 of the internal combustion engine also has a notification lamp 49.

The exhaust gas purification device 100 of the internal combustion engine has a control device 60. The detection signals from the exhaust temperature sensor 40 and the exhaust differential pressure detection unit 42 of the differential pressure sensor 41 are input to the control device 60. Further, the control device 60 includes an accelerator sensor 45 that detects the amount of operation of the accelerator pedal, a rotation speed sensor 46 that detects the engine rotation speed NE that is the rotation speed of the output shaft of the internal combustion engine, an ignition switch 47, and an engine body 10. An output signal from an air flow meter 48 or the like that detects the intake air amount Ga supplied to the engine is also input. The control device 60 includes a CPU, a ROM, and a RAM. The control device 60 executes filter regeneration control for burning and removing PM collected by the PM filter 31 and correction processing described later by executing the program stored in the ROM by the CPU.

As shown in FIG. 2, as functional units, the control device 60 includes an injection valve control unit 61, a first estimator calculation unit 62, a second estimator calculation unit 63, a PM deposit amount calculation unit 64, and a deviation storage unit 65. It has a start request determination unit 66, an execution unit 67, a PM combustion amount estimation unit 68, and an end request determination unit 69. Further, the control device 60 has an ignition switch operation determination unit 70, a reference point learning unit 71, an abnormality determination unit 72, a correction processing unit 73, and a notification unit 74 as functional units.

The injection valve control unit 61 calculates a target fuel injection amount Q, which is a target value of the fuel amount injected from the fuel injection valve 11, based on, for example, the output signals from the accelerator sensor 45 and the rotation speed sensor 46. Then, the fuel injection valve 11 is controlled so that the calculated target fuel injection amount Q is injected. When the target fuel injection amount Q is larger than the fuel amount that is the stoichiometric air-fuel ratio, all the fuel is not burned in the combustion chamber 10A, and the exhaust containing the unburned fuel is discharged from the first exhaust pipe 21 of the exhaust passage 20. Is discharged to.

The first estimator calculation unit 62 calculates the first estimator PMf as the estimated amount of PM deposited on the PM filter 31 based on the operating state of the internal combustion engine. The first estimator calculation unit 62 first starts from the engine body 10 per unit time based on the engine rotation speed NE detected by the rotation speed sensor 46 and the target fuel injection amount Q calculated by the injection valve control unit 61. The PM discharge amount, which is an estimated amount of PM discharged to the exhaust passage 20, is calculated. The larger the target fuel injection amount Q, the larger the amount of PM contained in the exhaust gas tends to be. Further, since the amount of exhaust gas discharged per unit time increases as the engine speed NE increases, the amount of PM discharged to the exhaust passage 20 per unit time tends to increase. In this way, the amount of PM contained in the exhaust gas changes according to the operating state of the internal combustion engine. The first estimator calculation unit 62 stores a map showing the relationship between the engine speed NE and the target fuel injection amount Q and the PM emission amount. This map has been obtained in advance by experiments and simulations. The first estimated amount calculation unit 62 calculates the first estimated amount PMf by integrating the calculated PM emission amount for each unit time. The first estimator calculation unit 62 subtracts the PM combustion amount calculated by the PM combustion amount estimation unit 68, which will be described later, from the integrated value while the filter regeneration control is being executed.

The second estimator calculation unit 63 calculates the second estimator PMc as the estimated amount of PM deposited on the PM filter 31 based on the front-rear differential pressure ΔP detected by the differential pressure sensor 41. The pressure loss in the exhaust passage 20 changes due to the accumulation of PM on the PM filter 31. That is, as the amount of PM accumulated in the PM filter 31 increases, the exhaust pressure on the upstream side of the exhaust tends to be higher than that of the PM filter 31 in the exhaust passage 20. As described above, in the exhaust passage 20, the front-rear differential pressure ΔP of the PM filter 31 and the amount of PM deposited on the PM filter 31 have a correlation. The front-rear differential pressure ΔP also reflects a change in the flow rate of the exhaust gas discharged from the engine body 10 of the internal combustion engine to the exhaust passage 20, that is, a change in the engine rotation speed NE of the internal combustion engine. Therefore, in the present embodiment, the second estimator calculation unit 63 rotates the engine when the intake air amount Ga flowing into the engine body, that is, the flow rate of the exhaust is sufficient and the front-rear differential pressure ΔP is correspondingly large. The second estimator PMc is calculated based on the front-rear differential pressure ΔP detected by the differential pressure sensor 41 when the operating region is stable with little change in the speed NE. The second estimator calculation unit 63 stores a map showing the relationship between the front-rear differential pressure ΔP calculated based on the output signal from the differential pressure sensor 41 and the second estimator PMc. This map was obtained in advance by experiments and simulations.

The deviation storage unit 65 subtracts the first estimator PMf calculated by the first estimator calculation unit 62 from the second estimator PMc when the second estimator PMc is calculated by the second estimator calculation unit 63. The calculated value is calculated and stored as a deviation ΔPM (= PMc-PMf).

The PM accumulation amount calculation unit 64 calculates the PM accumulation amount Pr, which is the amount of PM accumulated in the PM filter 31. The PM deposit amount calculation unit 64 is a case where the differential pressure sensor 41 is determined to be normal by the abnormality determination unit 72 described later, and the second estimator amount calculation unit 63 calculates the second estimator amount PMc. In the operating region, the larger of the first estimator PMf calculated by the first estimator calculation unit 62 and the second estimator PMc calculated by the second estimator calculation unit 63 is the PM deposition amount. Calculated as Pr. That is, when the first estimator PMf is equal to or greater than the second estimator PMc (PMf ≧ PMc), the PM deposit amount calculation unit 64 calculates the first estimator PMf as the PM deposit amount Pr (Pr = PMf). When the first estimated amount PMf is less than the second estimated amount PMc (PMf <PMc), the PM deposition amount calculation unit 64 calculates the second estimated amount PMc as the PM accumulation amount Pr (Pr = PMc). After that, when the second estimator calculation unit 63 is no longer in the operating region for calculating the second estimator PMc, the PM accumulation amount calculation unit 64 sets the deviation ΔPM and the first estimator stored in the deviation storage unit 65. The PM deposit amount Pr is calculated based on the first estimated amount PMf calculated by the calculation unit 62. That is, in the operating region where the second estimator PMc is calculated, when the second estimator PMc is equal to or less than the first estimator PMf and the deviation ΔPM stored in the deviation storage unit 65 is “0” or less, PM deposition. The amount calculation unit 64 calculates the first estimator PMf calculated by the first estimator calculation unit 62 as the PM deposit amount Pr after it is no longer in the operating region for calculating the second estimator PMc. Further, in the operating region where the second estimator PMc is calculated, when the second estimator PMc is larger than the first estimator PMf and the deviation ΔPM stored in the deviation storage unit 65 is larger than "0", PM After the accumulation amount calculation unit 64 is no longer in the operating region for calculating the second estimator PMc, the PM accumulation amount is the sum of the first estimator PMf calculated by the first estimator calculation unit 62 and the deviation ΔPM. Calculated as Pr.

Further, when the difference pressure sensor 41 is determined to be abnormal by the abnormality determination unit 72, the PM accumulation amount calculation unit 64 is not used by the second estimator PMc, but by the first estimator calculation unit 62. The calculated first estimator PMf is calculated as the PM deposition amount Pr. The PM accumulation amount calculation unit 64 adds the PM emission amount calculated by the first estimator calculation unit 62 to the PM accumulation amount Pr while executing the filter regeneration control, and also adds the PM combustion amount estimation unit to be described later. By subtracting the PM combustion amount calculated by 68 from the PM accumulation amount Pr, the PM accumulation amount Pr during execution of the filter regeneration control is calculated.

The start request determination unit 66 determines whether or not there is a start request for filter reproduction control. The start request determination unit 66 determines that there is a start request for filter regeneration control when it is determined that the PM accumulation amount Pr calculated by the PM accumulation amount calculation unit 64 is equal to or greater than the first predetermined amount. The first predetermined amount is set to an amount slightly smaller than the allowable upper limit value of the accumulated amount of PM in the PM filter 31. The first predetermined amount is obtained in advance by an experiment or a simulation and stored in the control device 60.

The execution unit 67 starts the filter reproduction control when it is determined by the start request determination unit 66 that there is a start request for the filter reproduction control. Further, after starting the filter regeneration control, the filter regeneration control is terminated when it is determined by the end request determination unit 69, which will be described later, that there is an end request for the filter regeneration control. In the filter regeneration control, for example, by controlling the injection valve control unit 61 so that the target fuel injection amount becomes larger than the fuel amount that becomes the stoichiometric air-fuel ratio, the exhaust gas containing the unburned fuel is discharged to the exhaust passage 20. To do so. The unburned fuel is burned by the oxidation reaction in the oxidation catalyst 30 to raise the temperature of the exhaust gas. When the exhaust gas having become hot enough to burn PM flows through the PM filter 31, the PM collected by the PM filter 31 is burned and removed. In the following, the temperature of the exhaust gas at which PM can be burned is referred to as a regeneration temperature.

The PM combustion amount estimation unit 68 calculates the PM combustion amount, which is the amount of PM burned and removed by the filter regeneration control. In the present embodiment, the PM combustion amount estimation unit 68 burns and removes the PM by the filter regeneration control based on the temperature of the exhaust gas in the second exhaust pipe 23 calculated based on the output signal from the exhaust temperature sensor 40. The amount of PM combustion, which is the amount, is calculated. A map showing the relationship between the temperature of the exhaust gas in the second exhaust pipe 23 and the amount of PM combustion is obtained and stored in advance by experiments and simulations.

The end request determination unit 69 determines whether or not there is an end request for filter reproduction control. After the start of the filter regeneration control, the end request determination unit 69 determines that there is an end request when the PM accumulation amount Pr calculated by the PM accumulation amount calculation unit 64 is equal to or less than the second predetermined amount. The second predetermined amount is set to an amount correspondingly smaller than the allowable upper limit value of the accumulated amount of PM in the PM filter 31 and smaller than the first predetermined amount. The second predetermined amount is obtained in advance by an experiment or simulation and stored in the control device 60.

The ignition switch operation determination unit 70 determines whether or not the ignition switch 47 has been switched from the on state to the off state and whether or not the ignition switch 47 has been switched from the off state to the on state based on the output signal from the ignition switch 47. Is determined.

The reference point learning unit 71 learns the reference point in the output signal of the differential pressure sensor 41. In the differential pressure sensor 41, the reference voltage when the front-rear differential pressure ΔP is “0” differs for each individual. Therefore, in the reference point learning unit 71, after the ignition switch 47 is switched from the on state to the off state and before the ignition switch 47 is switched from the off state to the on state, the front-rear differential pressure ΔP becomes almost 0. The reference point is learned based on the output voltage of the differential pressure sensor 41 in the state of being in the state, and the learning value for setting the reference point to a predetermined value is stored. As described above, the learning value is calculated based on the state of the differential pressure sensor 41 in the period from the stop of the internal combustion engine to the start of the start of the internal combustion engine.

The abnormality determination unit 72 is a differential pressure sensor based on the learning value learned by the reference point learning unit 71 when the ignition switch operation determination unit 70 determines that the ignition switch 47 has been switched from the off state to the on state. 41 abnormality determination is performed. In the present embodiment, the abnormality determination unit 72 determines that the differential pressure sensor 41 is abnormal when the learning value is equal to or greater than the upper limit determination value or the learning value is less than the lower limit determination value. As described above, since the learning value is calculated based on the state of the differential pressure sensor 41 in the period from the stop of the internal combustion engine to the start of the start of the internal combustion engine, the abnormality determination unit 72 determines the internal combustion engine. An abnormality determination of the differential pressure sensor 41 is performed based on the state of the differential pressure sensor 41 during the period from the stop of the internal combustion engine to the start of the start of the internal combustion engine.

The correction processing unit 73 sets the first estimator PMf as the second estimator when the internal combustion engine is started after the ignition switch 47 is switched from the off state to the on state by the ignition switch operation determination unit 70. A correction process for correction based on PMc is executed. The correction process is executed after the ignition switch 47 is switched from the off state to the on state and the abnormality determination unit 72 determines the abnormality of the differential pressure sensor 41. The correction processing unit 73 executes the correction process when the abnormality determination unit 72 determines that the differential pressure sensor 41 is normal, and does not execute the correction process when the difference pressure sensor 41 is determined to be abnormal. .. The start of the internal combustion engine is a period from the time when the ignition switch 47 is switched from the off state to the on state until the start of the internal combustion engine is completed. The start of the internal combustion engine ends when the complete explosion is completed and the internal combustion engine is in an idle operation state. Whether or not the idle operation state has been reached can be determined, for example, by whether or not the state in which the rotation speed of the internal combustion engine is higher than the predetermined rotation speed continues for a predetermined time.

When the deviation ΔPM stored in the deviation storage unit 65 is smaller than “0” (ΔPM <0), that is, when the first estimator PMf is larger than the second estimator PMc, the correction processing unit 73 is used. , The first estimated amount PMf is reduced and corrected in the correction process. In this case, the correction processing unit 73 first calculates the correction amount based on the deviation ΔPM.

As shown in FIG. 3, in the correction processing unit 73, a map showing the relationship between the deviation ΔPM and the correction amount is obtained and stored in advance by an experiment or a simulation. As shown in FIG. 3, the correction amount when the first estimated amount PMf is reduced and corrected is when the deviation ΔPM is small in the region from the deviation ΔPM from “0” to the predetermined amount P1 smaller than the “0”. The more it becomes. When the correction amount is calculated, the correction processing unit 73 calculates the corrected first estimator PMf by subtracting the correction amount from the first estimator PMf calculated by the first estimator calculation unit 62. In the region where the deviation ΔPM is from “0” to the predetermined amount P1, the correction amount is set to correct the first estimator PMf to a value equal to the second estimator PMc, and thereby, by the correction process, The value of the first estimator PMf becomes a value equal to the value of the second estimator PMc.

Further, as shown in FIG. 3, an upper limit is set for the correction amount of the first estimated amount PMf. That is, when the deviation ΔPM is a predetermined amount P1 or less, the correction amount does not change and becomes a value equal to the upper limit value Fu even if the deviation ΔPM becomes smaller. Since the upper limit of the correction amount is set in this way, when the difference between the first estimated amount PMf and the second estimated amount PMc is large and the deviation ΔPM is the predetermined amount P1 or less, the first correction process is performed once. The estimator PMf is not reduced to a value equal to the second estimator PMc.

Further, in the correction processing unit 73, when the deviation ΔPM stored in the deviation storage unit 65 is larger than “0” (ΔPM> 0), that is, the first estimator PMf is compared with the second estimator PMc. When the amount is small, the first estimated amount PMf is increased and corrected in the correction process. In this case, the correction processing unit 73 calculates the corrected first estimator PMf by adding a value equal to the deviation ΔPM to the first estimator PMf calculated by the first estimator calculation unit 62. As a result, in one correction process, the value of the first estimated amount PMf is corrected so as to be equal to the value of the second estimated amount PMc. In this way, the correction processing unit 73 sets an upper limit on the correction amount when the first estimated amount PMf is reduced and corrected. That is, when the deviation ΔPM is a predetermined amount P1 or less, the correction amount in one correction process is smaller than the correction amount required to eliminate the deviation by the deviation ΔPM. When the reduction correction of the 1 estimated amount PMf is performed, the correction degree of the first estimated amount PMf can be made smaller than that when the increase correction is performed.

In the first estimator calculation unit 62, when the first estimator PMf is corrected by the correction processing unit 73, the first estimator is estimated by integrating the PM emission amount with respect to the corrected first estimator PMf. Calculate PMf.

As shown in FIG. 2, when the abnormality determination unit 72 determines that the differential pressure sensor 41 is abnormal, the notification unit 74 turns on the notification lamp 49 to notify the abnormality.
A series of processing flows related to the correction processing executed by the control device 60 will be described with reference to the flowchart of FIG. This series of processes is executed at predetermined intervals.

As shown in FIG. 4, when the control device 60 starts this series of processes, the ignition switch operation determination unit 70 first determines whether or not the ignition switch 47 has been switched from the off state to the on state (step S400). .. When the start operation of the internal combustion engine is executed and the ignition switch 47 is switched from the off state to the on state, a positive determination is made in the process of step S400 (step S400: YES). In this case, the abnormality determination unit 72 then determines the abnormality of the differential pressure sensor 41 (step S401). In the ignition switch operation determination unit 70, when the state of the ignition switch 47 determined in the previous process is in the off state and the state of the ignition switch 47 determined in the current process is in the on state, the ignition switch 47 is turned on. It is determined that the off state has been switched to the on state.

In the process of step S401, the abnormality determination unit 72 determines the abnormality of the differential pressure sensor 41 based on the learning value learned by the reference point learning unit 71. This learning value is calculated during the period in which the ignition switch 47 is in the off state immediately before it is determined that the ignition switch 47 has been switched from the off state to the on state in the process of step S400. When the learning value is equal to or more than the upper limit determination value or less than the lower limit determination value, the abnormality determination unit 72 determines that the differential pressure sensor 41 is abnormal. In this case, the notification unit 74 lights the notification lamp 49 to notify the abnormality. When the learning value is less than the upper limit determination value and equal to or greater than the lower limit determination value, the abnormality determination unit 72 determines that the differential pressure sensor 41 is normal. In this way, when the abnormality determination unit 72 determines the abnormality of the differential pressure sensor 41 based on the state of the differential pressure sensor 41 during the period from the stop of the internal combustion engine to the start of the start of the internal combustion engine, it is corrected next. The processing unit 73 determines whether or not the differential pressure sensor 41 is determined to be normal by the abnormality determination unit 72 (step S402).

When the differential pressure sensor 41 is determined to be normal (step S402: YES), the correction processing unit 73 shifts to the processing of step S403 and executes the correction processing. In the correction process, first, it is determined whether or not the deviation ΔPM stored in the deviation storage unit 65 is smaller than “0” (step S403). In the process of step S403, when it is determined that the deviation ΔPM is smaller than “0” (step S403: YES), that is, when the first estimator PMf is larger than the second estimator PMc, the correction processing unit. 73 subtracts the correction amount calculated based on the deviation ΔPM from the first estimated amount PMf. As a result, the first estimated amount PMf is reduced and corrected (step S404). When the correction processing unit 73 reduces and corrects the first estimated amount PMf, the control device 60 ends a series of processing related to the correction processing.

Further, in the process of step S403, when it is determined that the deviation ΔPM is not smaller than “0” (step S403: NO), the correction processing unit 73 determines whether or not the deviation ΔPM is larger than “0”. (Step S405). In the process of step S405, when it is determined that the deviation ΔPM is larger than “0” (step S405: YES), that is, when the first estimator PMf is smaller than the second estimator PMc, the correction processing unit 73 Adds the deviation ΔPM to the first estimator PMf. As a result, the first estimated estimator PMf is increased and corrected (step S406). When the correction processing unit 73 increases and corrects the first estimated amount PMf, the control device 60 ends a series of processing related to the correction processing.

On the other hand, in the process of step S405, when it is determined that the deviation ΔPM is not larger than “0” (step S405: NO), that is, the value of the first estimator PMf and the value of the second estimator PMc are equal. In this case, the correction processing unit 73 does not correct the first estimator PMf. In this case, the control device 60 ends a series of processes related to this correction process without correcting the first estimated amount PMf. In the correction process, when the first estimated amount PMf is increased or decreased, the deviation storage unit 65 resets the deviation ΔPM to “0”. After that, when the second estimator calculation unit 63 becomes the operating region for calculating the second estimator PMc, the deviation storage unit 65 deviates based on the calculated second estimator PMc and the first estimator PMf. Calculate and store ΔPM.

Further, in the process of step S401, if the abnormality determination unit 72 determines that the differential pressure sensor 41 is abnormal, a negative determination is made in the process of step S402 (step S402: NO), and subsequent steps S403 to S403 to The correction process up to step S406 is not performed. After that, the control device 60 ends a series of processes related to this correction process.

Further, in the process of step S400, when it is determined that the ignition switch 47 has not been switched from the off state to the on state (step S400: NO), the control device 60 does not execute the subsequent process and performs the correction process. The series of such processes is completed. When the first estimator PMf is corrected by the processing of steps S404 and S406, the first estimator calculation unit 62 subsequently calculates the PM emission amount for each unit time based on the operating state of the internal combustion engine. Is integrated with the corrected first estimator PMf to calculate the first estimator PMf.

Next, a series of processing flows related to the filter regeneration control executed by the control device 60 will be described with reference to the flowchart of FIG. This series of processes is repeatedly executed at predetermined control cycles when the internal combustion engine is in an operating state.

As shown in FIG. 5, when this series of processes is started, the control device 60 first determines whether or not the differential pressure sensor 41 is normal (step S500). The series of processes related to the above-described regeneration process is executed when the internal combustion engine is started, and is executed at a timing earlier than this series of processes. Therefore, in the process of step S500, in the control device 60, the differential pressure sensor 41 is normal based on the result of the abnormality determination (process of step S401 in FIG. 4) executed by the abnormality determination unit 72 in the series of processes related to the reproduction process. It is determined whether or not it is.

In the process of step S500, when the control device 60 determines that the differential pressure sensor 41 is normal (step S500: YES), the control device 60 is operated in which the operating region of the internal combustion engine is calculated by the second estimated amount PMc. It is determined whether or not it is a region (step S501). When the front-rear differential pressure ΔP is correspondingly large and the engine rotation speed NE is stable, the control device 60 determines that the operating region is in which the second estimated amount PMc is calculated (step S501: YES), and step S502. Move to the processing of. In the process of step S502, the PM deposit amount calculation unit 64 calculates the larger value of the first estimated amount PMf and the second estimated amount PMc as the PM deposit amount Pr. After that, the deviation storage unit 65 calculates and stores the value obtained by subtracting the first estimator PMf from the second estimator PMc as the deviation ΔPM (step S503).

On the other hand, in the process of step S501, when it is determined that the second estimated amount PMc is not in the operation region to be calculated (step S501: NO), then the control device 60 is stored in the deviation storage unit 65. It is determined whether or not the deviation ΔPM is larger than “0” (step S504). When the deviation ΔPM is larger than “0”, a situation has already occurred in which the second estimator PMc is calculated after the deviation ΔPM is reset to “0” after the correction process is executed. It can be determined that the second estimator PMc calculated by the second estimator calculation unit 63 in the operating region at that time was larger than the first estimator PMf calculated by the first estimator calculation unit 62. Therefore, when a positive determination is made in the process of step S504 (step S504: YES), the PM accumulation amount calculation unit 64 adds the first estimated amount PMf and the deviation ΔPM stored in the deviation storage unit 65. The calculated value is calculated as the PM deposition amount Pr (step S505).

Further, when the differential pressure sensor 41 is determined to be abnormal in the process of step S500 (step S500: NO) and when a negative determination is made in the process of step S504 (step S504: NO), the PM deposition amount is calculated. Part 64 calculates the first estimated amount PMf as the PM deposition amount Pr (step S506).

When the PM deposition amount Pr is calculated in this way, the process proceeds to step S507, and the start request determination unit 66 determines whether or not there is a start request for filter regeneration control. When it is determined that the PM accumulation amount Pr is equal to or greater than the first predetermined amount and it is determined that there is a request to start the filter regeneration control (step S507: YES), the execution unit 67 starts the filter regeneration control. (Step S508). After that, the end request determination unit 69 determines whether or not there is an end request for the filter reproduction control (step S509). In the process of step S509, immediately after the start of the filter regeneration control, the PM combustion amount after the start of the filter regeneration control is small, so that the PM deposit amount Pr calculated by the PM deposit amount calculation unit 64 is the second predetermined amount. Is exceeded, and it is determined that there is no termination request (step S509: NO). If it is determined that there is no end request, the control device 60 repeatedly executes the process of step S509. After that, when a corresponding time elapses and the PM combustion amount after the filter regeneration control is started increases and the PM accumulation amount Pr calculated by the PM accumulation amount calculation unit 64 becomes equal to or less than the second predetermined amount, the process ends. It is determined that there is a request (step S509: YES). In this case, the process proceeds to the next step S510. In the process of step S510, the execution unit 67 ends the filter reproduction control. As a result, a series of processes related to filter reproduction control is completed.

Further, in the process of step S507, when the PM accumulation amount Pr is less than the first predetermined amount, the start request determination unit 66 determines that there is no start request for the filter regeneration control (step S507: NO). In this case, the control device 60 ends this series of processes without executing the subsequent processes from step S508 to step S510, that is, the filter reproduction control.

The operation and effect of this embodiment will be described with reference to FIGS. 6 and 7. First, a case where the differential pressure sensor is normal will be described with reference to FIG.
(1) As shown in FIG. 6A, when the ignition switch 47 is switched from the on state to the off state at the timing t610, the internal combustion engine is stopped. In this state, the reference point learning unit 71 learns the reference point in the output signal of the differential pressure sensor 41 and stores the learning value for setting the reference point as a predetermined value.

After that, when the ignition switch 47 is switched from the off state to the on state at the timing t611, the internal combustion engine is started, and the state is changed from the stopped state to the started state. After the timing t611, the starting state of the internal combustion engine is up to the timing t613 when the operating state of the internal combustion engine becomes the idle operation state. Further, the timing t613 or later when the operating state of the internal combustion engine becomes the idle operating state is referred to as a normal operating state. As described above, the control device 60 determines whether or not the operating state of the internal combustion engine is in the idle operation state based on whether or not the state in which the rotation speed of the internal combustion engine is higher than the predetermined rotation speed continues for a predetermined time. In the present embodiment, the time when the internal combustion engine is started means the period during which the internal combustion engine is in the started state.

When the internal combustion engine is started at the timing t611, a series of processes related to the regeneration process is executed, and the abnormality determination unit 72 first determines the abnormality of the differential pressure sensor 41. In the example shown in FIG. 6, since the differential pressure sensor 41 is normal, as shown in FIG. 6 (c), it is determined that the differential pressure sensor 41 is normal in the abnormality determination at the timing t611. Therefore, as shown in FIG. 6D, the notification lamp 49 does not light.

After that, at the timing t612 later than the timing t611, the correction processing unit 73 executes the correction processing. Immediately before the timing t610, the deviation ΔPM stored by the deviation storage unit 65 when the internal combustion engine is in the operating state is “0”. In this case, in the correction process executed at the timing t612, the value of the first estimator PMf and the value of the second estimator PMc are equal, so that the first estimator PMf does not change in the correction process.

As shown by the solid line in FIG. 6B, after the timing t611, the first estimator calculation unit 62 calculates the first estimator PMf based on the operating state of the internal combustion engine. From the timing t611 to the timing t614, the change in the engine rotation speed NE of the internal combustion engine is large, and the operating region is in which the second estimated amount PMc is not calculated. The deviation ΔPM stored by the deviation storage unit 65 is “0”. ". Therefore, when the PM deposit amount calculation unit 64 starts calculating the PM deposit amount Pr at the timing t611, the first estimated amount PMf is calculated as the PM deposit amount Pr thereafter.

At the timing t614, the front-rear differential pressure ΔP becomes correspondingly large and the engine rotation speed NE stabilizes, so that the front-rear differential pressure ΔP detected by the differential pressure sensor 41 and the amount of PM deposited on the PM filter 31 correlate with each other. It becomes the operating state of the internal combustion engine having. Therefore, the second estimator calculation unit 63 calculates the second estimator PMc based on the front-rear differential pressure ΔP detected by the differential pressure sensor 41. Since the value of the second estimator PMc is larger than that of the first estimator PMf shown by the alternate long and short dash line in FIG. 6 (b), the PM deposit amount calculation unit 64 is shown by the solid line in FIG. 6 (b). The second estimator PMc is calculated as the PM deposition amount Pr.

After that, at the timing t615, when the operating region in which the second estimator PMc is not calculated due to a change in the engine rotation speed NE of the internal combustion engine or the like, the second estimator calculation unit 63 performs a second based on the front-rear differential pressure ΔP. Stop calculating the estimator PMc. In the example shown in FIG. 6, the second estimator PMc is calculated in the period between timing t614 and timing t615. Then, when the second estimator PMc is calculated, the deviation storage unit 65 calculates and stores the deviation ΔPM obtained by subtracting the first estimator PMf from the second estimator PMc. The latest calculated deviation ΔPM will be stored. That is, the deviation ΔPM calculated at the timing t615 is stored as the deviation ΔPM (1). The deviation ΔPM (1) is larger than “0”. As a result, as shown by the solid line in FIG. 6B, the PM deposit amount calculation unit 64 calculates the value obtained by adding the deviation ΔPM (1) to the first estimated amount PMf as the PM deposit amount Pr after the timing t615. do.

As shown in FIG. 6A, when the ignition switch 47 is switched from the on state to the off state at the subsequent timing t616, the internal combustion engine is stopped. In this state, the reference point learning unit 71 again learns the reference point in the output signal of the differential pressure sensor 41, and stores the learning value for setting the reference point to a predetermined value. When the internal combustion engine is stopped, the PM accumulation amount Pr is not calculated, so the value is "0". Further, the control device 60 holds the values of the first estimated amount PMf and the deviation ΔPM (1) while the internal combustion engine is stopped.

After that, when the ignition switch 47 is switched from the off state to the on state at the timing t617, the internal combustion engine is started, and the state is changed from the stopped state to the started state. As a result, a series of processes related to the reproduction process is started, the abnormality determination of the differential pressure sensor 41 is executed at the timing t617, and the correction process is executed at the timing t618 later than the timing t617. Further, when the internal combustion engine is started, the PM deposit amount calculation unit 64 starts calculating the PM deposit amount Pr, and at the timing t617, the first estimated amount PMf held in the control device 60 and the deviation ΔPM (1) are set. The added value is calculated as the PM deposition amount Pr.

In the correction process, when the internal combustion engine immediately before the timing t616 is in the operating state (timing t611 to timing t616), the first estimator PMf is corrected based on the deviation ΔPM (1) stored by the deviation storage unit 65. In this correction process, since the deviation ΔPM (1) is larger than “0”, the first estimator PMf is increased so that the corrected value of the first estimator PMf is equal to the second estimator PMc. to correct. At the timing t618, the value of the second estimator PMc when the second estimator PMc is calculated by the second estimator calculation unit 63 at the timing t618 and the value of the first estimator PMf before correction The difference can be considered equal to the deviation ΔPM (1). Therefore, when the deviation ΔPM is added to the first estimator PMf, the corrected first estimator PMf is tentatively calculated by the second estimator calculation unit 63 at the timing t618. The value is equal to the second estimator PMc. In this way, by increasing the first estimator PMf before correction by the deviation ΔPM, the deviation between the first estimator PMf and the second estimator PMc is eliminated by one correction process, and the first estimation after correction is performed. The value of the quantity PMf can be equal to the second estimator PMc. That is, as shown by the alternate long and short dash line in FIG. 6B, the first estimated amount PMf increases at the timing t618. When the first estimated amount PMf is increased and corrected in this way, the deviation storage unit 65 resets the stored deviation ΔPM to “0”. At the timing t618, the second estimator PMc is not calculated and the deviation ΔPM is “0”. Therefore, the corrected first estimator PMf is calculated as the PM deposition amount Pr.

After the timing t618, the first estimator calculation unit 62 calculates the first estimator PMf by integrating the corrected first estimator PMf with the PM emission amount calculated based on the operating state of the internal combustion engine. Since the period from timing t618 to timing t619 is an operating region in which the second estimator PMc is not calculated, the PM deposition amount Pr increases as the first estimator PMf increases.

Then, as shown by the solid line in FIG. 6B, it is determined that there is a request to start the filter regeneration control at the timing t619 when the PM accumulation amount Pr becomes the first predetermined amount or more, and as shown in FIG. 6E. In addition, a series of processes related to filter regeneration control is started. When the filter regeneration control is started, the PM collected by the PM filter 31 is burned and removed, and the PM deposition amount Pr decreases as shown by the solid line in FIG. 6 (b).

Then, at the timing t620 when the PM deposition amount Pr becomes equal to or less than the second predetermined amount, the filter regeneration control is terminated as shown in FIG. 6 (e). After that, since the operating state of the internal combustion engine continues, as shown in FIG. 6B, the PM deposition amount Pr also increases as the first estimated amount PMf increases.

At the timing t621 when a corresponding time has passed from the timing t620, the operating state of the internal combustion engine becomes the operating state of the internal combustion engine in which the front-rear differential pressure ΔP and the amount of PM deposited on the PM filter 31 have a correlation. As a result, the second estimator calculation unit 63 calculates the second estimator PMc. At the timing t621, as shown by the alternate long and short dash line in FIG. 6B, the value of the second estimator PMc is smaller than that of the first estimator PMf. Therefore, the PM deposit amount calculation unit 64 calculates the first estimated amount PMf as the PM deposit amount Pr as shown by the solid line in FIG. 6B.

After that, when the ignition switch 47 is switched from the on state to the off state at the timing t622, the internal combustion engine is stopped. The second estimator PMc is calculated in the period from the timing t621 to the timing t622 when the internal combustion engine is stopped. The deviation storage unit 65 calculates and stores the deviation between the first estimated amount PMf and the second estimated amount PMc at the timing t622 as the deviation ΔPM (2). The deviation ΔPM (2) is a value smaller than “0”. Further, when the internal combustion engine is stopped, the reference point learning unit 71 again learns the reference point in the output signal of the differential pressure sensor 41, and stores the learning value for setting the reference point as a predetermined value. After the timing t622, since the internal combustion engine is in the stopped state, the PM accumulation amount Pr becomes “0”.

After that, when the ignition switch 47 is switched from the off state to the on state at the timing t623, the internal combustion engine is started, and the state is changed from the stopped state to the started state. As a result, a series of processes related to the reproduction process is started, the abnormality determination of the differential pressure sensor 41 is executed at the timing t623, and the correction process is executed at the timing t624 later than the timing t623. Further, when the internal combustion engine is started, the PM deposit amount calculation unit 64 starts calculating the PM deposit amount Pr. At the timing t623, since the deviation ΔPM (2) is a value smaller than “0”, the first estimated amount PMf held in the control device 60 is calculated as the PM accumulation amount Pr.

In the correction process at the timing t624, when the internal combustion engine immediately before the timing t622 is in the operating state (timing t617 to timing t622), the first estimator PMf is calculated based on the deviation ΔPM (2) stored by the deviation storage unit 65. to correct. In this correction process, since the deviation ΔPM (2) is smaller than “0”, the first estimator PMf is obtained by subtracting the correction amount calculated based on the map shown in FIG. 3 from the first estimator PMf. Make a weight loss correction. In this example, since the deviation ΔPM (2) is equal to or less than the predetermined amount P1, the correction amount is calculated to be equal to the upper limit value Fu. At the timing t624, the value of the second estimator PMc when the second estimator PMc is calculated by the second estimator calculation unit 63 at the timing t624 and the value of the first estimator PMf before correction The difference can be considered equal to the deviation ΔPM (2). The upper limit value Fu is a value smaller than the deviation ΔPM (2). Therefore, the first estimator PMf after the correction, which is obtained by subtracting the upper limit value Fu which is the correction amount from the first estimator PMf before the correction, tentatively calculates the second estimator PMc by the second estimator calculation unit 63 at the timing t624. The value is not equal to the second estimator PMc (≈ the second estimator PMc at the timing t622), but is larger than the second estimator PMc. After that, the first estimated amount PMf is calculated as the PM accumulated amount Pr until the operating region in which the second estimated amount PMc is calculated is reached. When the deviation ΔPM stored after the timing t624 is smaller than “0”, the first estimated amount PMf is reduced and corrected in the correction process executed when the internal combustion engine is started next time. By executing the correction processing a plurality of times in this way, the value of the first estimated amount PMf after the correction becomes a value equal to the second estimated amount PMc. As a result, the discrepancy between the first estimator PMf and the second estimator PMc is eliminated.

In the present embodiment, when the internal combustion engine is started, the first estimated amount PMf calculated based on the operating state of the internal combustion engine is converted into the second estimated amount PMc calculated based on the front-rear differential pressure ΔP of the PM filter 31. Correct based on. The front-rear differential pressure ΔP of the PM filter 31 is detected by the differential pressure sensor 41. As for the differential pressure sensor 41, since the abnormality is determined based on the state in the period from the stop of the internal combustion engine to the start of the internal combustion engine, the abnormality of the differential pressure sensor 41 is made at the timing when the internal combustion engine is started. It is appropriate to make a judgment. Therefore, if it is the timing when starting the internal combustion engine, it is possible to calculate the second estimator PMc supported by the fact that the differential pressure sensor 41 is normal, and the accuracy of the calculation of the second estimator PMc is guaranteed. It becomes possible to do. The first estimated amount PMf is calculated based on the operating state of the internal combustion engine, and has a wide operating range that can be calculated. On the other hand, when the front-rear differential pressure ΔP detected by the differential pressure sensor 41 and the amount of PM deposited on the PM filter 31 have a correlation, the operating area of the internal combustion engine is limited, so that the second estimated amount PMc The calculable operating range of is narrow. Since the influence of the amount of PM actually deposited on the PM filter 31 is reflected in the front-rear differential pressure ΔP of the PM filter 31, the second estimator PMc is compared with the first estimator PMf, and the PM filter 31 It is easy to reflect the actual amount of PM accumulated in. Therefore, the first estimator PMf, which has a wide calculable operating range, is corrected based on the second estimator PMc in consideration of the appropriate timing for determining the abnormality of the differential pressure sensor 41. When the 1 estimated amount PMf is corrected by the 2nd estimated amount PMc and the PM accumulated amount Pr is calculated, it is possible to suppress a decrease in the calculation accuracy of the PM accumulated amount Pr.

(2) In the above embodiment, when the first estimated amount PMf is increased and corrected at the timing t618, the first estimated amount PMf after the correction is equal to the second estimated amount PMc in one correction process. The estimator PMf is increased. On the other hand, when the first estimated amount PMf is reduced and corrected at the timing t624, the upper limit of the correction amount is set. That is, when the deviation ΔPM becomes a predetermined amount P1 or less, the correction amount in one correction process is smaller than the correction amount required to eliminate the deviation by the deviation ΔPM. Therefore, in this case, when the reduction correction of the first estimated amount PMf is performed, the correction degree of the first estimated amount PMf can be made smaller than that when the increase correction is performed. When the first estimator PMf is larger than the second estimator PMc, the first estimator PMf is used as the PM deposition amount Pr, which is a parameter for determining the execution of the filter regeneration control. Therefore, by reducing the degree of correction when the first estimated amount PMf is reduced and corrected, it is assumed that the accuracy of the second estimated amount PMc is lowered due to the influence of the disturbance of the differential pressure sensor 41 or the like. However, it is possible to suppress a sudden change in the PM deposition amount Pr. As a result, when the first estimator PMf is corrected based on the second estimator PMc, the corrected first estimator PMf is smaller than the amount of PM actually deposited on the PM filter. Can be suppressed, and the PM deposition amount Pr can be set appropriately.

(3) When the first estimated amount PMf is increased and corrected, the first estimated amount PMf is increased so that the corrected first estimated amount PMf becomes a value equal to the second estimated amount PMc in one correction process. .. Therefore, the calculated PM deposit amount Pr is actually calculated as compared with the configuration in which the correction process is executed a plurality of times until the value of the first estimated amount PMf becomes equal to the value of the second estimated amount PMc and the amount is gradually increased and corrected. It becomes easy to avoid a state where the amount of PM is less than the amount of PM accumulated in the PM filter at an early stage.

(4) In the above embodiment, when the first estimated amount PMf is reduced and corrected, an upper limit is set for the correction amount of the first estimated amount PMf in one correction process. As a result, the value of the first estimator PMf is less likely to be reduced to a value equal to the second estimator PMc in one correction process. Therefore, by executing the correction process a plurality of times, the value of the first estimator PMf is reduced. Can be gradually reduced to a value equal to the second estimator PMc. Therefore, it is possible to prevent the value of the corrected first estimated amount PMf from becoming lower than the value of the actual PM accumulation amount Pr due to the temporary disturbance of the detection signal of the differential pressure sensor 41 or the like. The setting of PM deposition amount Pr can be made appropriate.

(5) Next, with reference to FIG. 7, a case where an abnormality occurs in the differential pressure sensor 41 will be described as an example.
As shown in FIG. 7A, when the ignition switch 47 is switched from the on state to the off state at the timing t710, the internal combustion engine is stopped. In this state, the reference point learning unit 71 learns the reference point in the output signal of the differential pressure sensor 41 and stores the learning value for setting the reference point as a predetermined value.

After that, when the ignition switch 47 is switched from the off state to the on state at the timing t711, the internal combustion engine is started, and the state is changed from the stopped state to the started state. After the timing t711, the starting state of the internal combustion engine is up to the timing t713 when the operating state of the internal combustion engine becomes the idle operation state. Further, the timing t713 or later when the operating state of the internal combustion engine becomes the idle operating state is referred to as a normal operating state.

When the internal combustion engine is started at the timing t711, a series of processes related to the regeneration process is executed, and the abnormality determination unit 72 first determines the abnormality of the differential pressure sensor 41. In the example shown in FIG. 7, as shown in FIG. 7 (c), the differential pressure sensor 41 is determined to be normal in the abnormality determination at the timing t711. Therefore, as shown in FIG. 7D, the notification lamp 49 does not light.

After that, at the timing t712 later than the timing t711, the correction processing unit 73 executes the correction processing. In this correction process, the deviation ΔPM stored by the deviation storage unit 65 is “0”, and the value of the first estimator PMf and the value of the second estimator PMc are equal, so that the first estimator PMf is corrected. Not done.

As shown by the solid line in FIG. 7B, after the timing t711, the first estimator calculation unit 62 calculates the first estimator PMf based on the operating state of the internal combustion engine. From the timing t711 to the timing t714, the change in the engine rotation speed NE of the internal combustion engine is large, and the operating region is in which the second estimated amount PMc is not calculated. The deviation ΔPM stored by the deviation storage unit 65 is “0”. ". Therefore, when the PM deposit amount calculation unit 64 starts calculating the PM deposit amount Pr at the timing t711, the first estimated amount PMf is calculated as the PM deposit amount Pr thereafter.

At the timing t714, the front-rear differential pressure ΔP becomes correspondingly large and the engine rotation speed NE stabilizes, so that the front-rear differential pressure ΔP detected by the differential pressure sensor 41 and the amount of PM deposited on the PM filter 31 correlate with each other. It becomes the operating state of the internal combustion engine having. Therefore, the second estimator calculation unit 63 calculates the second estimator PMc based on the front-rear differential pressure ΔP detected by the differential pressure sensor 41. After that, at the timing t716, when the operating region in which the second estimator PMc is not calculated due to a change in the engine rotation speed NE of the internal combustion engine or the like, the second estimator calculation unit 63 performs a second based on the front-rear differential pressure ΔP. Stop calculating the estimator PMc.

In this way, the second estimator calculation unit 63 calculates the second estimator PMc based on the front-rear differential pressure ΔP detected by the differential pressure sensor 41 during the period from the timing t714 to the timing t716. At the timing t714, the second estimator PMc is smaller than the first estimator PMf, but at the timing t716, the second estimator PMc is larger than the first estimator PMf. Therefore, at the timing t715 between the timing t714 and the timing t716, the second estimator PMc becomes equal to the first estimator PMf. In the period from timing t714 to timing t715, the value of the first estimator PMf is larger than that of the second estimator PMc shown by the alternate long and short dash line in FIG. 7 (b). As shown, the PM deposit amount calculation unit 64 calculates the first estimated amount PMf as the PM deposit amount Pr. Further, in the period from timing t715 to timing t716, the value of the second estimator PMc is larger than that of the first estimator PMf shown by the alternate long and short dash line in FIG. 7 (b). As shown in, the PM deposit amount calculation unit 64 calculates the second estimated amount PMc as the PM deposit amount Pr.

When the second estimator PMc is calculated, the deviation storage unit 65 calculates and stores the deviation ΔPM obtained by subtracting the first estimator PMf from the second estimator PMc. The latest calculated deviation ΔPM will be stored. That is, the deviation storage unit 65 stores the deviation ΔPM at the timing t716. This deviation ΔPM is larger than “0”.

After the timing t716, the operating region is such that the second estimated amount PMc is not calculated, and the deviation ΔPM stored by the deviation storage unit 65 is larger than “0”. Therefore, as shown by the solid line in FIG. 7B, the PM deposit amount calculation unit 64 calculates the value obtained by adding the deviation ΔPM to the first estimated amount PMf as the PM deposit amount Pr after the timing t716. Then, as shown in FIG. 7A, when the ignition switch 47 is switched from the on state to the off state at the timing t717, the internal combustion engine is stopped. In this state, the reference point learning unit 71 again learns the reference point in the output signal of the differential pressure sensor 41, and stores the learning value for setting the reference point to a predetermined value. When the internal combustion engine is stopped, the PM accumulation amount Pr is not calculated, so the value is "0". Further, the control device 60 holds the values of the first estimated amount PMf and the deviation ΔPM while the internal combustion engine is stopped.

After that, when the ignition switch 47 is switched from the off state to the on state at the timing t718, the internal combustion engine is started, and the state is changed from the stopped state to the started state. As a result, a series of processes related to the regeneration process is started, and the abnormality determination of the differential pressure sensor 41 is executed at the timing t718. As shown in FIG. 7C, in this example, in the abnormality determination at the timing t718, the learning value is equal to or higher than the upper limit value, and the abnormality determination unit 72 determines that the differential pressure sensor 41 is abnormal. .. In this way, when the abnormality determination unit 72 determines that the differential pressure sensor 41 is abnormal, the notification lamp 49 lights up to notify the abnormality, as shown in FIG. 7D.

Further, since the abnormality of the differential pressure sensor 41 is determined, the PM deposit amount calculation unit 64 calculates the first estimated amount PMf as the PM deposit amount Pr regardless of the deviation ΔPM. Therefore, the PM deposition amount Pr (= first estimated amount PMf) at the timing t718 is smaller than the PM deposition amount Pr (= first estimated amount PMf + deviation ΔPM) at the timing t717.

Further, since the abnormality of the differential pressure sensor 41 is determined, the correction process is not performed, and if the differential pressure sensor 41 is normal, the correction process is performed at the timing t719. It does not change. After the timing t719, the PM deposition amount Pr increases as the first estimated amount PMf increases.

Then, as shown by the solid line in FIG. 7B, it is determined that there is a request to start the filter regeneration control at the timing t720 when the PM accumulation amount Pr becomes the first predetermined amount or more, and as shown in FIG. 7E. In addition, a series of processes related to filter regeneration control is started. When the filter regeneration control is started, the PM collected by the PM filter 31 is burned and removed, and the PM deposition amount Pr decreases as shown by the solid line in FIG. 7 (b).

Then, at the timing t721 when the PM deposition amount Pr becomes equal to or less than the second predetermined amount, the filter regeneration control is terminated as shown in FIG. 7 (e). After that, since the operating state of the internal combustion engine continues, as shown in FIG. 7B, the PM deposition amount Pr also increases as the first estimated amount PMf increases.

After that, at the timing t722 when a corresponding time has elapsed from the timing t721, the second estimator calculation unit 63 becomes an operating region in which the second estimator PMc can be calculated. Even in this case, since the differential pressure sensor 41 is determined to be abnormal, the PM deposit amount calculation unit 64 calculates the first estimated amount PMf as the PM deposit amount Pr.

After that, when the ignition switch 47 is switched from the on state to the off state at the timing t723, the internal combustion engine is stopped.
In the present embodiment, it is determined that the differential pressure sensor 41 is normal, correction processing is performed when the accuracy of the second estimator PMc is guaranteed, and the differential pressure sensor 41 is determined to be abnormal. Therefore, when the accuracy of the second estimator PMc is not guaranteed, the correction process is not performed. Therefore, when the first estimator PMf is corrected based on the second estimator PMc, the corrected first estimator PMf reflects the actual PM deposition amount as compared with the first estimator PMf before the correction. Can be the value.

This embodiment can be modified and implemented as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
-In the above embodiment, the PM accumulation amount calculation unit 64 calculates the first estimated amount PMf as the PM accumulation amount Pr when the abnormality determination unit 72 determines that the differential pressure sensor 41 is abnormal. .. Instead of such a configuration, in the PM deposit amount calculation unit 64, even when the difference pressure sensor 41 is determined to be abnormal by the abnormality determination unit 72, the second estimator calculation unit 63 is the second estimator amount. When it is the operating region for calculating PMc, it is possible to adopt a configuration in which the larger value of the first estimator PMf and the second estimator PMc is calculated as the PM deposition amount Pr.

-In the above embodiment, the correction processing unit 73 executes the correction processing when the abnormality determination unit 72 determines that the differential pressure sensor 41 is normal, and determines that the differential pressure sensor 41 is abnormal. Sometimes the correction process was not executed. Such a configuration does not necessarily have to be provided. That is, it is also possible to adopt a configuration in which the correction process is executed in a state where the differential pressure sensor 41 is determined to be abnormal. For example, when the execution timing of the abnormality determination in the abnormality determination unit 72 and the start timing of the correction processing are close to each other, the information is transmitted to the correction processing unit after the differential pressure sensor 41 is determined to be abnormal by the abnormality determination. It may be the start timing of the correction process before reaching 73. In such a case, the correction process may be performed after the abnormality determination of the differential pressure sensor 41 is made.

-In the above embodiment, when the correction processing unit 73 reduces and corrects the first estimated amount PMf, the upper limit is set for the correction amount in one correction process, but the upper limit does not necessarily have to be set. In this case, it may be calculated so that the smaller the deviation ΔPM, the larger the correction amount so that the value becomes an appropriate value for eliminating the deviation ΔPM.

-The correction amount when the first estimated amount PMf is reduced and corrected is calculated based on the deviation ΔPM, but the calculation mode of this correction amount can be changed as appropriate. For example, the correction amount may be calculated as a fixed value regardless of the deviation ΔPM.

-When the first estimator PMf is subtracted and corrected, the correction amount calculated based on the deviation ΔPM is subtracted from the first estimator PMf, but this is the correction mode when the first estimator PMf is subtracted and corrected. Not limited to. For example, the deviation ΔPM (<0) may be added to the first estimated amount PMf without calculating the correction amount based on the deviation ΔPM. In this configuration, when the first estimated amount PMf is reduced and corrected, the value of the corrected first estimated amount PMf can be set to a value equal to the second estimated amount PMc in one correction process.

-In the above embodiment, when the correction processing unit 73 increases and corrects the first estimated amount PMf, the deviation ΔPM is added to the first estimated amount PMf, so that the corrected first estimated amount PMf in one correction process is performed. The value of is equal to the second estimator PMc. In order to make the value of the corrected first estimator PMf equal to the second estimator PMc, for example, a correction amount based on the deviation ΔPM is calculated, and the correction amount is added or multiplied by the first estimator PMf. Method may be adopted.

-In the above embodiment, when the correction processing unit 73 increases and corrects the first estimated amount PMf, the value of the corrected first estimated amount PMf is set to a value equal to the second estimated amount PMc in one correction process. I made it. The correction mode when the first estimated amount PMf is increased and corrected is not limited to this. For example, when the first estimated amount PMf is increased and corrected, the value of the corrected first estimated amount PMf is increased to a value equal to the second estimated amount PMc by executing the correction processing a plurality of times. May be good. In such a configuration, for example, a configuration is adopted in which a correction amount in the increase correction is calculated based on the deviation ΔPM and an upper limit is set for the correction amount. According to this configuration, the upper limit of the correction amount is set to be less than the required correction amount required to eliminate the deviation by the deviation ΔPM, so that the correction amount in one correction process is smaller than the required correction amount. Also reduce. As a result, the value of the corrected first estimator PMf is prevented from increasing to a value equal to the second estimator PMc in one correction process. Further, by setting a fixed value smaller than the deviation ΔPM as the correction amount, the value of the first estimated amount PMf after correction is prevented from increasing to a value equal to the second estimated amount PMc in one correction process. Is also possible.

-In the above embodiment, the correction processing unit 73 corrects the value of the first estimated amount PMf so as to be equal to the value of the second estimated amount PMc. That is, a value equal to the second estimated amount PMc was set as the target value of the corrected first estimated amount PMf. The mode for setting the target value of the first estimated amount PMf after correction in the correction processing unit 73 is not limited to this. For example, the correction processing unit 73 can set a value larger or smaller than the second estimated amount PMc as the target value of the corrected first estimated amount PMf in the correction processing unit 73. In such a configuration, if the target value of the first estimated amount PMf is limited, it is possible to set an upper limit or a lower limit for the correction degree when correcting the first estimated amount PMf by the correction process. That is, by limiting the degree of correction, it is possible to limit the value that the corrected first estimated amount PMf can take to a predetermined range.

-In the above embodiment, the correction processing unit 73 performs correction processing based on the deviation ΔPM stored before the internal combustion engine is started and when the internal combustion engine is in the operating state. The deviation ΔPM subjected to the correction processing in the correction processing unit 73 is not limited to the one stored before the internal combustion engine is started. For example, if the second estimator PMc can be calculated between the start of the internal combustion engine and the start of the correction process, the deviation ΔPM between the second estimator PMc and the first estimator PMf is used. It is also possible to execute the correction process.

The second estimator calculation unit 63 is when the intake air amount Ga flowing into the engine body, that is, the flow rate of the exhaust is sufficient and the front-rear differential pressure ΔP is correspondingly large, and the change in the engine rotation speed NE is small. The second estimator PMc was calculated based on the front-rear differential pressure ΔP detected by the differential pressure sensor 41 when the operating region was stable. Instead of such a configuration, the second estimator calculation unit 63 may always calculate the second estimator PMc regardless of the operating state of the internal combustion engine. In this case, it is desirable that the deviation storage unit 65 stores the deviation ΔPM in a state where the accuracy of the second estimator PMc calculated by the second estimator calculation unit 63 can be guaranteed.

-In the above embodiment, when the first estimated amount PMf is larger than the second estimated amount PMc, the first estimated amount PMf is reduced and corrected in the correction process, but the present invention is not limited to this configuration. For example, even when the first estimator PMf is larger than the second estimator PMc, if it is necessary to correct it to a value close to the actual PM accumulation amount, the first estimation is performed in the correction process. It is also possible to increase and correct the amount PMf. Further, in the above embodiment, when the first estimated amount PMf is smaller than the second estimated amount PMc, the first estimated amount PMf is increased and corrected in the correction process, but the present invention is not limited to this configuration. For example, even when the first estimator PMf is smaller than the second estimator PMc, if it is necessary to correct it to a value close to the actual PM accumulation amount, the first estimation is performed in the correction process. It is also possible to reduce the amount PMf.

-In the above embodiment, when the reduction correction of the first estimated amount PMf is performed, the correction degree of the first estimated amount PMf is made smaller than that when the increase correction is performed. The degree of correction when correcting the first estimated amount PMf can be changed as appropriate. For example, when the reduction correction of the first estimated amount PMf is performed, the correction degree of the first estimated amount PMf may be larger than that when the increase correction is performed, or these correction degrees may be equalized.

The abnormality determination unit 72 determines the abnormality of the differential pressure sensor 41 based on the learning value learned by the reference point learning unit 71, but the mode of abnormality determination is not limited to this. That is, the abnormality determination unit 72 may determine the abnormality of the differential pressure sensor 41 based on the state of the differential pressure sensor 41 during the period from the stop of the internal combustion engine to the start of the internal combustion engine. For example, the internal combustion engine. It is also possible to perform an abnormality determination by comparing the output voltage of the differential pressure sensor 41 with the determination value during the period from the stop of the internal combustion engine to the start of the start of the internal combustion engine.

-In the above embodiment, the abnormality determination unit 72 determines the abnormality at the start of the internal combustion engine in which the ignition switch 47 is switched from the off state to the on state. The timing of abnormality determination in the abnormality determination unit 72 is not limited to this. For example, it is possible to determine the abnormality of the differential pressure sensor 41 at a timing later than when the internal combustion engine is started or when the internal combustion engine is stopped.

-In the above embodiment, the PM accumulation amount calculation unit 64 becomes the operating region in which the second estimator PMc is calculated by the second estimator calculation unit 63, and then the second estimator calculation unit 63 becomes the second estimator. When it is no longer in the operating region for calculating PMc, the PM deposition amount Pr is calculated based on the deviation ΔPM stored in the deviation storage unit 65 and the first estimator PMf calculated by the first estimator calculation unit 62. However, it is possible to omit such a configuration. For example, when the second estimator calculation unit 63 is in the operating region where the second estimator PMc is calculated, and then the second estimator calculation unit 63 is no longer in the operating region where the second estimator PMc is calculated. Regardless of the deviation ΔPM, the first estimator PMf may be calculated as the PM deposition amount Pr.

-In the above embodiment, an example in which the differential pressure sensor is configured by the exhaust differential pressure detection unit 42, the upstream side detection passage 43, and the downstream side detection passage 44 is shown, but the configuration of the differential pressure sensor can be changed as appropriate. be. For example, the downstream side detection passage 44 of the differential pressure sensor may be opened to the atmosphere without being connected to the third exhaust pipe 25. In this case, the pressure on the downstream side of the exhaust gas from the PM filter 31 is regarded as the atmospheric pressure, and the front-rear differential pressure of the PM filter 31 is detected. Further, a first pressure sensor for detecting the pressure on the upstream side of the exhaust from the PM filter 31 and a second pressure sensor for detecting the pressure on the downstream side of the exhaust from the PM filter 31 are provided, and the first pressure sensor and the second pressure are provided. It is also possible to adopt a differential pressure sensor that detects the front-rear differential pressure of the PM filter 31 based on the difference between the detection signal and the sensor.

-In the above embodiment, the control device 60 executes the filter reproduction control and the correction process by executing the program stored in the ROM by the CPU. That is, the exhaust purification device 100 of the internal combustion engine includes a program storage device such as a ROM that stores all programs for executing filter regeneration control and correction processing, and a processing device such as a CPU that executes processing according to the program. In preparation for this, filter playback control and correction processing are executed by executing software processing. The exhaust gas purification device 100 of the internal combustion engine is not limited to the one that performs the above-mentioned various controls only by software processing in this way. For example, a dedicated hardware circuit that executes at least a part of the software processing executed in the above embodiment may be provided. This configuration can be realized, for example, by including a processing device and a program storage device that execute a part of the processing executed in the above embodiment according to a program, and a dedicated hardware circuit that executes the remaining processing. Further, for example, it can be realized by providing a dedicated hardware circuit that executes all the processes executed in the above embodiment. In this way, the processing required for the various controls may be executed by the processing circuit including at least one of one or a plurality of software processing circuits and one or a plurality of dedicated hardware circuits.

10 ... Engine body, 10A ... Combustion chamber, 11 ... Fuel injection valve, 20 ... Exhaust passage, 21 ... First exhaust pipe, 22 ... First catalytic converter, 23 ... Second exhaust pipe, 24 ... Second catalytic converter, 25 ... Third exhaust pipe, 30 ... Oxidation catalyst, 31 ... PM filter, 40 ... Exhaust temperature sensor, 41 ... Differential pressure sensor, 42 ... Exhaust differential pressure detection unit, 43 ... Upstream detection passage, 44 ... Downstream detection passage, 45 ... Accelerator sensor, 46 ... Rotation speed sensor, 47 ... Ignition switch, 48 ... Airflow meter, 49 ... Notification lamp, 60 ... Control device, 61 ... Injection valve control unit, 62 ... First estimation amount calculation unit, 63 ... 2 Estimated amount calculation unit, 64 ... PM accumulation amount calculation unit, 65 ... Deviation storage unit, 66 ... Start request determination unit, 67 ... Execution unit, 68 ... PM combustion amount estimation unit, 69 ... End request determination unit, 70 ... Ignition Switch operation determination unit, 71 ... Reference point learning unit, 72 ... Abnormality determination unit, 73 ... Correction processing unit, 74 ... Notification unit, 100 ... Internal combustion engine exhaust purification device.

Claims (4)

A PM filter that is installed in the exhaust passage of an internal combustion engine and collects PM contained in the exhaust,
It is equipped with a differential pressure sensor that detects the front-rear differential pressure, which is the difference between the pressure on the exhaust upstream side of the PM filter and the pressure on the exhaust downstream side of the PM filter.
The first estimated amount is calculated as the estimated amount of PM accumulated in the PM filter based on the operating state of the internal combustion engine, and is accumulated in the PM filter based on the front-rear differential pressure detected by the differential pressure sensor. It is an exhaust gas purification device for an internal combustion engine that calculates the second estimated amount as the estimated amount of PM.
An abnormality determination of the differential pressure sensor is performed based on the state of the differential pressure sensor during the period from the stop of the internal combustion engine to the start of the start of the internal combustion engine.
When starting the internal combustion engine, a correction process for correcting the first estimated amount based on the second estimated amount is executed.
The larger of the first estimated amount and the second estimated amount is calculated as the PM accumulated amount, and when the PM accumulated amount is equal to or more than a predetermined amount, the PM collected by the PM filter is burned and removed. start the filter regeneration control for,
When the first estimator is larger than the second estimator, the first estimator is reduced and corrected in the correction process, and when the first estimator is smaller than the second estimator, the correction process is performed. In the correction process, the first estimator is increased and corrected.
An exhaust gas purification device for an internal combustion engine that reduces the degree of correction of the first estimated amount when performing the reduction correction as compared with the case of performing the increase correction. When the first estimator is increased and corrected, the value of the first estimator after correction in one correction process is set to a value equal to the second estimator.
The exhaust gas purification device for an internal combustion engine according to claim 1. When the first estimated amount is reduced and corrected, an upper limit is set for the correction amount of the first estimated amount in one correction process.
The exhaust gas purification device for an internal combustion engine according to claim 1 or 2. When the differential pressure sensor is determined to be normal by the abnormality determination, the correction process is executed, and when the differential pressure sensor is determined to be abnormal, the correction process is not executed.
The exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 3.

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